Hello,
I'm thinking about PRS-700, but I'm from the Czech republic.. I'd like to ask, if is it possible to read books in Czech language, which has special characters like these ěčřýáíé. Can ereader show them.

Hello,
I'm thinking about PRS-700, but I'm from the Czech republic.. I'd like to ask, if is it possible to read books in Czech language, which has special characters like these ěčřýáíé. Can ereader show them.

Can one chenge the fonts used?

Thanks in advance

It's not officially supported, but you can change the default font on the PRS-505, and I believe the PRS-700. What you can definitely do is embed fonts in EPUB books, guaranteeing that glyphs for all the characters in the book are available.

Yes you can change the fonts, we just do not know how at the moment ;-).
Do not worry. Our resident hackers have alredy something done, they just do not want to release it, because at the moment there is no way to unbrick the device if something goes wrong.

Now seriously.
You can still read Czech (or ANY language of your choice) books on the device.
Even without updating fonts.
Just create a pdf file with page size 90mm x 115mm
and do not forget to embed fonts into the document.
You can download Sony Library software and see what will your document look like on a Reader.